Although overshadowed by the en banc Federal Circuit arguments inTheraSense v. Becton Dickinsonthis morning,Cancer Research Technology v. Barr Laboratoriesmay provide a preview of what the opinions in TheraSense could look like - although it doesn't necessarily indicate which view of inequitable conduct will ultimately prevail. InCancer Research, Judges Lourie and Newman reversed a district court finding of prosecution laches and inequitable conduct, while dissenting Judge Prost would have reached the opposite result.

The patent at issue (the '291 patent) involved a set of thirteen tetrazine derivatives that the original 1982 specification identified as possessing anticancer activities based on animal studies. During the first nine years of prosecution, the examiner repeatedly rejected the claims due to lack of utility; rather than file a response to the office actions, the applicant instead filed continuation after continuation. In 1991, Cancer Research obtained ownership of the patent application and shortly thereafter responded to the examiner's arguments. The patent issued in 1993 and expires in 2014.

Following Cancer Research's clinical testing, the FDA approved one of the compounds covered by the '291 patent (marketed as TEMODAR) for the treatment of one type of cancer in 1999 and a second in 2005. In 2007, Barr Laboratories filed an Abbreviated New Drug Application ("ANDA") for a generic form of TEMODAR. Cancer Research sued Barr for infringement four months later. During the district court proceedings, the parties stipulated to validity and infringement and, after a bench trial, the courtfound that the patent was unenforceable due to prosecution laches and inequitable conduct.

Prosecution LachesGiven the nearly ten-year delay before any meaningful response to the examiner's rejection was filed, Barr contended that the patent was unenforceable due to prosecution laches. The district agreed, concluding that the delay in prosecution was unreasonable and unexplained.

On appeal, the majority reversed the finding of prosecution laches, holding that the doctrine requires not just unreasonable delay, but also a showing of prejudice. The majority further held that "to establish prejudice, an accused infringer must show evidence of intervening rights, i.e., that either the accused infringer or others invested in, worked on, or used the claimed technology during the period of delay." (Slip Op. at 9). Here, there was no evidence of intervening rights during the prosecution period, such as evidence showing that someone other than the patent holder attempted to develop the claimed compounds. Even Barr itself waited until 2007 - four years later than required - before filing its ANDA. The majority also noted that there was no public harm: in the absence of the patent, Cancer Research likely would not have been incentivized to develop TEMODAR at all.

Writing in dissent, Judge Prost rejected the notion that prosecution laches requires prejudice, let alone intervening rights; rather, under her reading of the precedent such a requirement is not part of the laches determination. Furthermore, in her opinion, both Barr and the public were harmed by Barr's inability to market a generic version of TEMODOR.

Comment: I'm unconvinced by Judge Prost's argument on this point. If she is correct, then the '291 patent was never enforceable - be it in 2007, when Barr filed its ANDA, or 1993, when it issued. Yet without an enforceable patent, Cancer Research would never have developed TEMODOR, let alone engaged in the expensive Phase III clinical studies necessary to demonstrate its safety and efficacy. Thus, the "harm" to the public would been greater in the absence of the '291 patent, not less."